No abstract

The marigolds (Tagetes spp.) in this study were classified as excluders for cadmium (Cd); however, their leaves also accumulated substantial Cd content. Among the experimental treatments (i.e., control, cattle manure, pig manure, and leonardite which served as soil amendments), pig manure resulted in significantly increased growth performance for all marigold cultivars as seen by relative growth rates (119–132.3%) and showed positive effects on leaf anatomy modifications, e.g., thickness of spongy and palisade mesophyll, size of vein area and diameter of xylem cells. This may be due to substantially higher essential nutrient content, e.g., total nitrogen (N) and extractable phosphorus (P), in pig manure that aided all marigold cultivars, particularly the French cultivar which exhibited the highest relative growth rate (132.3%). In the Cd-only treatment, cell disorganization was observed in vascular bundles as well as in palisade and spongy mesophyll, which may have been responsible for the lowest plant growth performance recorded in this study, particularly among the American and Honey cultivars (RGR = 73% and 77.3%, respectively).

The marigolds (Tagetes spp.) in this study, were classified as excluders for cadmium (Cd); however, their leaves also accumulated substantial Cd content. Among the experimental growth media (i.e., control, cattle, pig manure, and leonardite served as soil amendments), pig manure was found to result in significantly increased growth performance for all marigold cultivars, as seen by relative growth rates (119-132.3%) and showed positive effects on leaf anatomy modifications e.g., thickness of spongy and palisade mesophyll, size of vein area and diameter of xylem cells. This may be due to substantially higher essential nutrient content, e.g., total N and extractable P, in pig manure that aided all marigold cultivars particularly the French cultivar which exhibited the highest relative growth rate (132.3%). In the Cd only treatment, cell disorganization was observed in vascular bundles as well as in palisade and spongy mesophyll, which may have been causal in returning the lowest plant growth performances recorded in this study, particularly in the American and Honey cultivars (RGR = 73% and 77.3%, respectively).